Preparation of beta-alanine



Patented Jan. 14, 1947 UNITED STATE s PATENT OFFlCE 1 2,414,389 ranraiiarlon or BETA-ALANINE Joseph H. Paden, Glenbrook, Coma,

American 'Cyanami 11 Company,

assignor to New York,

N. Y., a corporation of Maine I No Drawings.

iClaims.

Application June 25, 1942, erlal No. 448,488

This invention relates to the preparation or beta-aminopropionic iacid (beta-alanine) and more particularly, to. the preparation 01 betaaminopropionic acid in one step from hydracrylic acid and ammonium hydroxide.

According to the present invention I have found thathydracrylic acid and ammonium hydroxide, when heated together in a pressure vessel at temperatures ranging from about 120 C. to about 225 C. for from about one to about twentysolution was cooled. clarified, filtered evaporated to a stifl, syrupy consistency and dissolved in 3 volumes of methanol. Twenty-one parts of betaaminopropionic acid crystallized out. The yield was 13.5%.

Example 2 158 parts (1:15 mols) of hydracrylic team parts of 28% ammonium hydroxide, 756 parts of four hours, react to produce beta-aminopropionic ly practicable method of preparing this intermediate is indicated. The process of the present invention provides such a method.

It is an advantage of the present invention that the only reactants essential for the operation of the process are hydracrylic acid and ammonium hydroxide. The latter is, of course, readily avail- .able and cheap; the former is not disproportionately expensive and may be obtained by the alkaline hydrolysis of ethylene cyanohydrin.

It is another advantage of the present invention that the reaction involved is simple, easily controlled, and takes place in a single step. Thus, beta-aminopropionic acid may be produced directly from hydracryllc acid without requiring the isolation of any intermediate product.

It is a further advantage of the invention that the beta-aminopropionic acid is obtained in good yield in a form which permits easy separation from the reaction mixture.

The invention will be described in greater detail in conjunction with the following specific examples. It should be understood that these examples are merely specific embodiments oi the invention and it is not intended to limit the scope of the invention to the specific details therein set forth. Parts are by weight unless otherwise stated.

Example 1 158 parts (1.75 mols) of hydracryllc amino parts of 28% ammonium hydroxide, '756 parts of water and 2 parts or diphenylamine were heated in an autoclave at150 C. for one hour. The solution was cooled, clarified, filtered, evaporated to a stiff, syrupy consistency and dissolved in methanol and the beta-aminopropionic acid crystallized'out. The yield was 13%.

Example 3 g 158 parts (1.75 mols) of hydracrylic acid, 420

parts of 28% ammonium hydroxide, 756 parts of water and 2 parts of diphenylamine were heated in an autoclave at 125 C. for eight hours. The solution was cooled, clarified, filtered, evaporated to a stiff, syrupy consistency and dissolved in methanol and the beta-aminopropionic acid crystallized out. The yield was about 5%.

7 Example 4' 158 parts (1.75 mols) oi hydracrylic acid, 420

parts of 28% ammonium hydroxide, 756 parts of water and 2 parts of diphenylamine were heated in an autoclave at 125 C. for four hours. The

solution was cooled, clarified, filtered, evaporated to a stifl, syrupy consistency and dissolved in methanol and the beta-aminopropionic acid crystallized out. The yield was about 5%.

Example 5 After recovery of the beta-aminopropionic acid as described in Example 1, the filtrate was evaporated to reclaim the methanol. The resulting syrupy residue was heated with an additional amount of ammonium hydroxide at 200 C. for four hours and the solution treated as described in Example 1. A similar further yield of betaamlnopropionic acid crystals was obtained.

Apparently an equilibrium-is reached in thereaction between hydracrylic acid and ammonium hydroxide which may account for the fact that the residue from one operation may be used as the reactant in another with no appreciable decrease -in the yield of beta-aminopropionic acid obtained. When over-all yields are considered, this feature of my process is extremely important since yields approaching the theoretical may be obtained by reworking the residues.

Further evidence for the existence of an equilibrium mixture was, obtained from a series of further reactions wherein concentrations of the reactants, time of heating and temperature were varied within wide limits. The strength of the ammonium hydroxide was varied from 2% to scribed above, it may be desirable in some in- 28% with similar variations in the proportion of hydracrylic acid based on the proportion of ammonia; the .time or heating. from one to twentyfour hours; and the temperature, from 125 to 250 C. In all cases beta-aminopropionic acid was obtained but only drastic changes in the concentration o1 reactants gave more than a yield. For example, very low concentrations 01'- hydracrylic acid produced beta-aminopropionic acid in yields 01 the order of %-60% but the increased cost 01' removing'the larger volumes of solvent present would probably neutralize the economical advantages resulting from the increased yields.

The beta-aminopropionic acid produced by my process may, ii desired, be converted to an acid salt such as the hydrochloride or to a salt of "a metal such as an alkali or alkaline earth metal, and isolated in this form. I prefer, however, to isolate the beta-aminopropionic acid directly from the concentrated syrupy reaction product by diluting it with absolute methanol. When so isolated, the beta-aminopropionic acid is in a pure form and may then, if desired, be converted to the salts when they are required as intermediates in processes for producing pantothenic acid.

Methanol appears to be peculiarly suited for the above isolation or crystallization step. Attempts to dilute with various other aliphatic alcohols such ethanol or propanol have been unsatisfactory.-

In the reaction between hydracrylic acid and ammonium hydroxide under the conditions destances to add other substances to the reaction mixture. For example, dehydration catalysts. ammonium salts of weak acids such as ammonium carbonate, inhibitors, anti-oxidants, and other suitable reagents for slightly altering the course or speed oi the reaction may be added.

I claim:

1. The process of producing beta-aminopropionic acid which comprises reacting hydracrylic acid with aqueous ammonia at a temperature of from about 120 C. to about 225 C.

2. The process of producing beta-aminopropionic acid which comprises heating hydracrylic acid andaqueous ammonia at a temperature oi from about 150 C. to about 200 C. for from about one to about twenty-four hours.

3. The process of pionic acid which comprises reacting hydracrylic acid with aqueous ammonia at a temperature of from about C. to about 225 C. for from about one to about twenty-four hours, concentrating the reaction mixture to a syru and diluting the syrup with methanol to cause precipitation of beta-aminopropionic acid.

4. The process oi producing beta-aminopropicnic acid which comprises reacting hydracrylic acid with aqueous ammonia at a temperature of from about 120 C. to about 225 about one to about twenty-four hours, concentrating the reaction mixture to a syrup, diluting the syrup 'with methanol, collecting the precipi tated beta-aminopropionic acid,- concentrating the residue, and reacting said residue with aqueous ammonia at a 120 temperature of from about 0. to about 225 C. for from about one to about twenty-four hours to produce a further quantity of beta-aminopropionic acid.

JOSEPH H. PADEN.

producing beta-aminopro- C. for from 

